photo by Dawn Carrie CC BY-NC
Freshwater Jawless Leech

Leeches are dark-colored segmented worms living in lakes and ponds. Only a small minority attach themselves and suck the blood of warm-blooded mammals, and their bite is harmless. They take very little blood, don't transmit disease, and will fall off voluntarily when they finish eating. Others feed on snails, worms, and fish eggs and some scavenge.

There are over 650 species of leeches in North America. Most of them live in freshwater and prefer calm, shallow water where they can attach themselves to underwater rocks and plants. They swim by swaying from side to side or by pulling themselves along with the suckers at either end of their body. Their sharp cutting beaks are located within the head sucker.

Leeches are both male and female. They mate by twining around each other and trading sperm packets.

Did you know? Some leeches are very good parents. They cover the eggs with their body and fan them to protect them from fungus or bacteria. When the eggs hatch, the young hang from their parents and are carried from meal to meal.